The genus Capsicum belongs to the large family of the Solanaceae. Several species of the Capsicum group are valuable crops that are grown in open fields or under protected conditions in many countries all over the world. Capsicum species with pungent fruits are generally used as a spice, either fresh, dry or extracted. Species with non-pungent fruits in a big variety of shapes and colours, commonly known as sweet peppers, are widely used as vegetable.
The genus Capsicum can be divided in two distinct groups based on the flower colour: the white-flowered group, comprising e.g. the closely related species C. annuum, C. frutescens, C. baccatum, C. chacoense, C. galapagoense, C. praetermissum and C. chinense, and the purple-flowered group, comprising e.g. C. tovarii, C. pubescens, C. eximium and C. cardenasii. Of the white-flowered group Capsicum annuum, and its closely related species C. frutescens are the best known domesticated species, which are mainly used for the production of sweet and hot peppers for processing and consumption.
Capsicum, like other plants, is attacked by many pests and diseases, including insects, nematodes, fungi, bacteria and viruses. One of such bacterial diseases is bacterial leafspot, caused by the bacterium Xanthomonas campestris pv. vesicatoria. Bacterial leafspot of Capsicum can be recognized by numerous angular spot on the leaves. Initially, the spots are water-soaked. Leaves infected at an early stage become deformed. Often the margins of affected leaves are rimmed with a narrow band of necrotic tissue. Infected Capsicum leaves drop prematurely, by which the fruit is exposed to sun which may result in sun scald, secondary fruit rots and reduced yields. Capsicum fruits rarely show symptoms but may drop if infected early.
X. vesicatoria is widespread and damaging to Capsicum in particular in field-grown crops in warm-temperate and tropical countries, and thus has a large economic impact. Control of the disease relies principally on the production of plants from healthy (treated) seeds and on preventive steps taken during the entire season.
Useful resistances to such diseases, as well as other traits such as fruit quality characteristics etc., may exist in wild or other domesticated species of Capsicum, such as for example in C. pubescens which carries unique and specific traits, such as the resistance against certain races of the bacterium Xanthomonas vesicatoria, that are not present in the white flowering species. It thus may be advantageous to transfer such favourable genetic traits, such as any resistance gene, from the distinctly related purple-flowered C. pubescens to the commonly used white-flowered species such as C. annuum and/or C. frutescens. 
It is well known, however, that strong crossing barriers of varying degree exist between the different species of the Capsicum genus. Some crosses have even been proven impossible, and other crosses are only possible with the help of in vitro culture techniques, such as embryo rescue. In addition, in most cases the products derived from said crosses are completely or partially sterile which makes them not accessible for any further breeding purposes.
A need therefore exists for a method by which desirable genetic traits can be transferred between the different purple and white flowered Capsicum species.